1. Technical Field
One or more embodiments of the present invention relate to a power module to be built particularly in high power products such as a solid state relay and a power supply.
2. Background Art
A power module of this kind is configured such that an insulating substrate made of ceramic or the like, a heat plate made of a metal plate, one surface side of which is joined to one surface of the insulating substrate, a power module substrate which is joined to the other surface of the insulating substrate and formed with a circuit pattern, a power semiconductor element disposed on the circuit pattern of the power module substrate, and an external connecting terminal electrically connected to the power semiconductor element via the circuit pattern are sealed by means of a molding resin layer in a state where one end portion of the external connecting terminal and the other surface of the heat plate are exposed to the outside.
Then, a conventional power module of this kind is configured having, for example as shown in FIG. 16, an insulating substrate “a” made of ceramic or the like, a heat plate b made of a metal plate, one surface side of which is joined to one surface of the insulating substrate “a”, and a power module substrate c which is joined to the other surface of the insulating substrate “a” and formed with a circuit pattern (not shown).
A power semiconductor element d is disposed on the circuit pattern of the power module substrate c, while a pair of external connecting terminals e, f each exhibiting a curved shape so as to be electrically connected to the power semiconductor element d are set up on a surface of the power module substrate c.
Then, the insulating substrate “a”, the heat plate b, the power module substrate c, the power semiconductor element d and the external connecting terminals e, f constitute a power module pre-product g.
The power module pre-product g is set inside a cavity j formed of an upper molding die h and a lower molding die i as resin molding dies, and then sealed by a molding resin layer formed by filling the inside of the cavity j with a molten resin in a state where externally exposed end portions e-1, f-1 on one end sides of the external connecting terminals e, f and the other surface side of the heat plate b are each exposed to the outside, so as to be configured as a power module serving as a product (see Patent Literature 1).
In the case of setting the power module pre-product g inside the cavity j so as to be sealed by the molding resin layer, the power module pre-product g has been positioned such that aligning holes e-2, f-2 provided in the externally exposed end portions e-1, f-1 are fitted respectively with aligning pins i-1, i-1 provided in the lower molding die i through use of the externally exposed end portions e-1, f-1 of the external connecting terminals e, f extending in a horizontal direction and being exposed to the outside from the molding resin layer in the figure.
However, the power module, as a product manufactured by sealing the power module pre-product g by the molding resin layer, is configured such that, when combined with the externally exposed end portions e-1, f-1 of the external connecting terminals e, f (each having the shape of a protrusion in a horizontal direction from the molding resin layer in the figure), the heat plate b made of a metal plate protrudes in the horizontal direction from the surface to protect the insulating substrate “a,” which is vulnerable to a shock inside the cavity j so as to become areally large compared to the insulating substrate “a.” Thus, an insulating distance between each of the externally exposed end portions e-1, f-1 and the heat plate b is short, and there is little choice but to enlarge the product size to ensure the insulating properties.
Therefore, the present applicant proposes a power module as described in Patent Literature 2.
That is, as shown in FIG. 17, such a power module is similar to above-mentioned Patent Literature 1 in that it is configured having a heat plate b made of a metal plate, one surface side of which is joined to one surface of an insulating substrate “a” made of ceramic or the like, and a power module substrate c which is joined to the other surface of the insulating substrate “a” and formed with a circuit pattern (not shown), and in that a power semiconductor element d is disposed on the circuit pattern of the power module substrate c while a pair of external connecting terminals e, f electrically connected to the power semiconductor element d are set up on the surface of the power module substrate c, to constitute a power module pre-product g, but the external connecting terminals e, f have been formed in linear shape, to be set up in a standing manner in an orthogonal direction to the surface of the power module substrate c, while the heat plate b has been made areally smaller than the insulating substrate “a”. In addition, symbol m denotes a bonding body to electrically connect between one power module substrate c and the power semiconductor element d.
The power module having such a configuration can be provided as a product which sufficiently ensures the insulating distance between each of the external connecting terminals e, f and the heat plate b, and can also satisfy social demand for minimization of the size of the power module itself as a product.    Patent Literature 1: Japanese Unexamined Patent Publication No. 2007-165588    Patent Literature 2: Japanese Unexamined Patent Publication No. 2009-59812
However, in the power module shown in FIG. 17, when the power module pre-product g is to be set inside the cavity j and formed by the upper molding die h and the lower molding die i in order to seal the power module pre-product g by means of the molding resin layer. The protruding part of the insulating substrate “a” cannot be taken as an aligning region despite such a protrusion of the insulating substrate “a”. This is, because the insulating substrate “a” is very vulnerable to a shock and may be damaged, for example, due to cracking or breakage by being brought into contact with the lower molding die i. Thus, the protruding part of the insulating substrate “a” cannot be used as an aligning means inside the cavity j of the power module pre-product g.
The conventional art thus has an issue providing a product in practical use, which is to be solved for satisfying demand for minimization of the power module pre-product g, and by extension, minimization of the power module itself by making the heat plate b areally small with respect to that of the insulating substrate “a”.